This invention relates to archery bows and, in particular, to a limb pocket for an archery bow.
Archery bows are available in a variety of forms such as long bows, recurve bows, compound bows, and others. This invention is directed to those archery bows wherein the limbs can be separated from the handle and is specifically directed to overcome the difficulties that may be encountered in the manufacture, mounting, adjustment, and use of limbs attached to a bow handle.
A recurve bow or a compound bow is typically made in three pieces: an elongated, rigid handle and a pair of limbs. The limbs overlap the ends of the handle a short distance and are cantilever mounted to the ends of the handle. A pocket at each end of the handle receives the end of a limb. Each limb is held in place by a limb bolt passing through a hole or slot in the butt of the limb and engaging a threaded bore in the handle. The hole or slot does not closely fit around the limb bolt, which is used for adjusting the draw weight of the bow.
A transverse, semi-circular trough at the outer end of each pocket receives a half-round member having its flat side facing the underside of the limb. As used herein, the "underside" or "inside" of a limb is the side facing an archer holding a drawn bow. The "outside" surface of a limb is the generally convex side facing the target. The underside of the limb does not touch the pocket but rests on the member, which serves as a pivot for the limb as the limb bolt is tightened or loosened and as the bow is drawn and fired. The distance from the pivot to the free end of the limb is considerably greater than the distance from the pivot to the limb bolt. The large forces in the bow are therefore concentrated at the limb pocket.
There are problems with this construction of a bow. A first problem is that the placement of the limb is critical. Any slight misalignment of the limb increases the shear forces on the pocket and may cause the limb to rub and wear in the pocket. Abrasion of the butt of a limb may lead to cracking or splintering of the limb at the limb bolt if the misalignment is not corrected.
A compound bow differs from a long bow in that a block and tackle mechanism is used to bend the bow: pulleys or wheels are attached at the free ends of the limbs to obtain a mechanical advantage in bending the bow. The limbs can be made approximately three times as stiff as for a longbow of the same draw weight. Eccentrically mounted wheels enable one to use a much higher maximum draw weight because they provide a substantial "let off" or reduction in the holding force of a drawn bow.
The combination of stiffer limbs and greater draw weight applies large forces to the components of a compound bow and these forces can have a moment from the centerline of the bow and/or from the plane of a drawn bowstring. The forces from the bowstring and cables wound on the wheels may not align with the mounting of the limb to the handle, e.g. because of the way the bowstring and cables are wound or because of a sideward force caused by a finger release or a sideward force due to a cable guard. The result is a force tending to move the free ends of the limbs from side to side when the bow is drawn and/or fired. Thus, the structure for attaching the limbs to the handle must be substantial enough to resist these forces in order for the bow to perform consistently. Whether for target shooting or for hunting, archers continually strive for consistent technique. If a bow does not perform consistently, this effort is pointless.
In view of the foregoing, it is therefore an object of the invention to provide an improved limb attachment for an archery bow.
Another object of the invention is to provide a pocket having a resilient liner for receiving the butt of a bow limb.
A further object of the invention is to provide a pocket for a bow limb having low friction bearing surfaces for receiving the butt of a bow limb.